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102
METALLURGY OF IRON AND STEEL.
rotary form. This fault may be partly overcome by having the blast introduced from, the upper surface, but the waste of iron is greater, and the extra expense wipes away all advantages of a reduced cost of installation.
TABLE VI-A. Chemical History, of an Acid Bessemer Charge.
Illinois Steel Company, South Chicago, 111., August 13, 1890, F. Julian.
Barometer, 29.79 inches; temperature, 36° C. (96.8° F.); blast pressure, 27 pounds.   No
allowance for- leakage and clearance.   Weight of pig, 22,500 pounds.
Subject.	Initial Charge.	Time of Blowing.					
		2m. Os.	3m. 20s.	6m. 3s.	8m. 8s.	to-  10s' Spiegel-	
	2.98 0.94 0.43 .10 .06	2.94 0.63 0.09 0.104 0.06 42.40 5.63 40.29 4.31 6.54 1.22 1  :o.36 0.008 0.009 Silicon flame. 34502	2.71 0.33 0.04 0.106 0.06 50.26 5.13 34.24 0.96 7.90 0.91 0.34 0.008 0.009 brightening. 36028	1.72 0.03 0.03 0.106 0.06 62.54 4.06 21.26 1.93 8.79 0.88 0.34 0.010 0.014 m'der'te carbon flame. 53481	0.53 0.03 0.01 0.107 0.06 63.56 3.01 21.39 2.63 8.88 0.90 0.36 0.014 0.008 full carbon flame. 45365	0.04 0.03 0.01 0.108 0.06	0.45 0.038 1.15 0.109 0.059 62.20 2.76 17.44 2.90 13.72 0.87 0.29 0.010 . 0.011
							
							
Phosphorus ..................							
Sulphur ......................							
							
							
							
							
							
							
							
							
							
Flame ................						flame drops. 26430	
							
Cubic f eet o f air ......							
							
							
The lining is of stone, brick, or other refractory material and is about one foot thick. The bottom is either of brick or rammed plastic material, the tuyeres being of brick, from 20 to 26 inches in length,with holes" from three-eighths to one-half inch in diameter. The total tuyere area varies at different works from 2.0 to 2.5 square inches per ton of charge. The blast pressure may be 30 pounds per square inch during the first period of the blow, but there has been a tendency toward greater tuyere area and a reduction in the pressure to about 20 pounds or less. In a very hot charge, or if the slag is sloppy, the pressure must sometimes be reduced to 10 pounds after the flame "breaks through" (i.e., after the carbon begins to burn), to prevent the expulsion of ineta.1 from the nose. The blowing engine and the tuyere openings being proportionate to the work in hand, the h,eats, whether heavy or light, are usually blown in from 7 to 12 minutes.'
SEC. VIb.—Chemical history of a charge.—-The chemical history of a charge was investigated by F. Julian, of the Illinois Steel Company, and his results are given in Table VI-A, which is copied